That appears to change things. If an FM3 has not been issued yet, you are still without an immigration document since your application has your FMT attached. You should have the FMT to travel. If it has expired, you can still get a letter of permission while the FM3 is in process. If none of that applies, I suppose you could simply walk out of Mexico and re-enter the USA with your passport, call the lawyer and cancel your application. Of course, you can't fly out without a current immigration document, so you will probably have to take a bus to the border and walk across. I know nothing of fines going out and you wouldn't be stopping at Mexican immigration, outbound, unless you had an FM3 to be stamped.